This invention relates to surveillance assemblies and, in particular, to surveillance assemblies which are adapted to accommodate environmental
Surveillance assemblies are known in which the surveillance assembly comprises a dome-shaped support housing to which is joined or attached a dome-shaped cover member or "bubble". The support housing and cover member define an enclosed space for receiving a camera and lens assembly which views outward of the surveillance assembly through the cover member. Usually, the camera and lens assembly is supported in the surveillance assembly so as to be rotational about a vertical axis for effecting a panning movement and to be pivotable about a horizontal axis to effect a tilting movement.
When the surveillance assembly is intended to be used in environments in which there are wide variations in temperature (as, for example, when it is to be used outdoors), various additions have been made to the assembly in an attempt to reduce any adverse effects which might result from the wide temperature changes. These additions have sought to cool the assembly to compensate for high environmental temperatures and to heat the assembly to compensate for low environmental temperatures. In this way, overheating of the electrical components of the assembly, fogging within the assembly and/or icing of the dome-shaped cover member are avoided.
A surveillance assembly having such compensation for environmental conditions is disclosed in U.S. Pat. No. 4,320,949. In a first embodiment of the surveillance assembly of the `949 patent, a thermostatically controlled fan is disposed in the side wall of the upper support housing. This fan provides forced air circulation in the housing to cool the housing when the temperature in the housing reaches a predetermined level. Also included in this embodiment of the surveillance assembly are thermostatically controlled heaters. The latter are brought into operation when the temperature in the housing approaches freezing so as to heat the air in the housing.
In a second embodiment of the surveillance assembly of the `949 patent, air is brought into the assembly by natural circulation. In this embodiment, a space or inlet area is provided at the interface of the support housing and cover member so that air can naturally enter the support housing about the circumference of the housing. This air is circulated downward adjacent the inner wall of the cover member and then proceeds upward into the support housing where it is exhausted through an air exhaust port.
Another surveillance assembly in which heating and cooling of the assembly is provided to compensate for environmental changes in temperature is disclosed in U.S. Pat. No. 4,984,089, assigned to the same assignee hereof. The surveillance assembly of the `089 patent attempts to improve on the above-discussed compensation system of the `949 patent.
In the assembly of the `089 patent, an air in-take valve and air exhaust valves are disposed in the side wall and top wall of the support housing, respectively. Exhaust fans are also disposed in the support housing for causing air to be exhausted from the assembly via the exhaust valves which are in the issuance paths of the exhaust fans.
A circulation fan and a heater unit are additionally included in the assembly in the area of the cover member. This fan provides forced air to the inner wall of the cover member through a slot in a shroud. The shroud is situated in front of the cover member and the slot in the shroud permits the camera and lens assembly to view outward of the surveillance assembly.
The surveillance assembly of the `089 patent is further provided with a control unit which provides control signals for the exhaust fans, circulation fan and heater assembly. The control unit causes continuous operation of the circulation fan and includes a thermostat circuit which provides first and second signals for operating the exhaust fan and heater assembly upon the occurrence of first and second temperatures.
While the aforesaid elements in the surveillance assembly of the `089 patent satisfactorily compensate for environmental temperature changes, the manner of compensation has certain limitations. First, at any particular time, forced air is directly applied only to the region of the inner wall of the cover member aligned with the slot in the shroud. As a result, a region of the inner wall which is removed from the slot may not receive an adequate amount of forced air until the camera and lens assembly and, hence, the slot in the shroud are actually aligned with the region. This could cause delay in viewing outward of the assembly if, for example, the region is found to be partially fogged or iced when the camera and lens assembly arrives at the region.
Secondly, the circulation fan and heater unit of the surveillance assembly of the `089 patent are mounted to a plate which carries the camera and lens assembly. This is necessary so that the forced air from these elements remains aligned with the slot in the shroud which is also attached to the plate so that the shroud moves with the camera and lens assembly. In some surveillance assembly arrangements, such as the arrangement disclosed in copending patent application U.S. Ser. No. 761,331 and issued U.S. Pat. No. 5,223,872, both of which are also assigned to the same assignee hereof, this is not practical due to size and power constraints.
It is, therefore, a primary object of the present invention to provide a surveillance assembly of the above-type which does not suffer from the above disadvantages.
It is a further object of the present invention to provide a surveillance assembly of the above-type in which compensation for environmental changes is more readily and easily carried out.
It is also an object of the present invention to provide a surveillance assembly of the above type meeting the above-stated objectives and which can better accommodate various configurations of the camera and lens assembly, including the camera and lens assembly of the `331 application and `872 patent.